1. Field of the Invention
The present invention relates to a polymer matrix resin and a fiber reinforced composite material comprising said matrix.
2. Description of Related Art
Polymer resin matrices are known which have a moderate glass transition temperature (Tg) of around 125° C. These matrices may also demonstrate excellent fatigue properties at room temperature (RT) when combined with specific fibers to form a composite material. An example of one such matrix is HexPly® M10R which is available from Hexcel Composites Limited (Duxford, Cambridge, UK). The fatigue properties of such matrices will diminish as the service temperature increases from RT.
In some circumstances, for example in automotive applications, a matrix resin having a high Tg is desired which also demonstrates excellent fatigue properties at room and elevated temperatures when combined with specific fibers. An increase in Tg is typically achieved by increasing the crosslink density (1/Xn) of the cured matrix resin. However, an increase in 1/Xn adversely affects the inherent toughness of the matrix. The concomitant fatigue performance of the matrix resin when it is combined with specific fibers is thus, also adversely affected.
In an attempt to overcome this problem and to increase the toughness of the matrix resin, toughening components have been added to matrix resin compositions. While this does improve fatigue properties, other matrix resin properties such as Tg, strength and modulus tend to be adversely affected. Furthermore, processing conditions are made more severe as a result of an increase in matrix resin viscosity caused by the presence of additional tougheners. Therefore, improvements in fatigue performance have previously been achieved but at the expense of other physical and mechanical properties of the matrix and processing options.
Therefore, it is desirable to produce a matrix resin which has a high Tg i.e. around 150° C. and a composite material comprising said matrix which when cured has excellent fatigue properties at RT and elevated temperatures. For vehicle (i.e. cars, trucks and buses) leaf spring applications, 90° C. is a typical elevated temperature.